Method for Locating and Measuring Deformations in a Work of Civil Engineering

• US 20070279632A1
• Filed: 03/24/2004
• Published: 12/06/2007
• Est. Priority Date: 03/24/2004
• Status: Active Grant

• Current Assignee: Fiber Optic Sensors & Sensing Systems, Ten Cate Geosynthetics France
• Original Assignee: Fiber Optic Sensors & Sensing Systems, Ten Cate Geosynthetics France
• Inventors: Delmas, Philippe, Nancey, Alain, Voet, Marc, Vlekken, Johan, Schoubs, Els
• Granted Patent: US 7,532,780 B2
• Time in Patent Office: Days
• US Class Current: 356/429
• CPC Class Codes: E02D 1/00 Investigation of foundation soil in situ investigation involving boring or specially adapted to earth drilling E21B25/00, E21B49/00; investigating or analysing materials by determining their chemical or physical properties, in general G01N, e.g. sampling G01N1/00
• CPC Class Codes: G01B 11/165 by means of a grating deformed by the object
• CPC Class Codes: G01B 11/18 using photoelastic elements

Abstract

The invention concerns a process for locating and measuring deformation in a civil engineering structure, characterised by the fact that at least one geosynthetic fabric (1) containing a plurality of optical fibres (2a to 2e) in parallel and capable of transmitting signals is applied in the said structure or under the said structure,

the said optical fibres containing Bragg gratings (3), evenly spaced in series (4) of N1 consecutive gratings that correspond to the same wavelength, the said series being themselves distributed in identical sets, each of which contains N2 consecutive series that correspond to the different wavelengths, and by the fact that, in at least two optical fibres, the numbers N1 of gratings of a series and the numbers N2 of series (4) of a set (5) are determined in such as way that the measurement of the differences between the wavelengths of the incident light transmitted in each of the said optical fibres and the wavelengths of the light reflected by the Bragg gratings enable to locate the deformations to which the structure is subjected on the one hand and, on the other, to measure the elongation of the said optical fibres where the deformation occurs.

Claims

1. Process for locating and measuring deformations in a civil engineering structure, characterised by the fact that at least one geosynthetic fabric (1) containing a plurality of optical fibres (2a to 2e) in parallel and capable of transmitting signals is applied in the said structure or under the said structure,

the said optical fibres containing Bragg gratings (3), evenly spaced in series (4) of N1 consecutive gratings that correspond to the same wavelength, the said series being themselves distributed in identical sets, each of which contains N2 consecutive series that correspond to different wavelengths, and by the fact that, in at least two optical fibres, the numbers N1 of gratings of a series and the numbers N2 of series (4) of a set (5) are determined in such as way that the measurement of differences between the wavelengths of the incident light transmitted in each of the said optical fibres and the wavelengths of the light reflected by the Bragg gratings enable to locate the deformations to which the structure is subjected on the one hand and, on the other, to measure the elongation of the said optical fibres where the deformation occurs.

2. Process according to claim 1, characterised by the fact that in at least two optical fibres, the numbers N1 of gratings of a series (4) are equal, and the numbers N2 of series (4) of a set (5) are prime to each other.

3. Process according to claim 1, characterised by the fact that in at least one optical fibre, the number N1 of gratings in a series is equal to the number of gratings of a set in another optical fibre.

4. Geosynthetic fabric for the application of the process according to any one of the claims 1 to 3, characterised by the fact that it contains a plurality of optical fibres (2a to 2e) in parallel, the said optical fibres containing Bragg gratings (3), evenly spaced in series (4) of N1 consecutive gratings that correspond to the same wavelength, the said series (4) being themselves distributed in identical sets (5) of N2 consecutive series that correspond to different wavelengths.

5. Geosynthetic fabric according to claim 4, characterised by the fact that the optical fibres (2a to 2e) include a sheath to protect them against shear failure, due to aggressive agents in the soil, and against corrosion.

6. Geosynthetic fabric according to one of the claims 4 or 5, characterised by the fact that the optical fibres (2a to 2e) are laid in the direction of the length of the said geosynthetic fabric.

7. Geosynthetic fabric according to any one of the claims 4 to 6, characterised by the fact that the optical fibres are inserted in the said geosynthetic fabric during its manufacture.